ZIP Code 21133 — Randallstown, MD
21133 is a standard (street delivery) ZIP code serving Randallstown, Maryland, in Baltimore County. To mail something here you only need these five digits — but the four-digit extension narrows delivery to a single point, and it is what USPS bulk postage discounts are priced on.
ZIP code 21133 at a glance
| ZIP code | 21133 |
|---|---|
| Primary city | Randallstown |
| State | Maryland (MD) |
| County | Baltimore FIPS 24005 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 31,398 |
| Coordinates | 39.377050, -76.811740 |
How ZIP+4 works in 21133
The four digits after the hyphen encode a delivery segment inside 21133. In practice one segment usually means:
- One side of one block — odd numbers on a street between two cross streets
- A single large building, or one floor of it
- A group of PO boxes, sometimes a single box
- A single business that receives enough mail to warrant its own code
That is why 21133 has no single ZIP+4: two neighbors across the street from each other usually have different ones. Enter a street address above and we will return the exact nine-digit code along with the standardized USPS address format.
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 21133.
| ZIP | City | Distance |
|---|---|---|
| 21244 | Windsor Mill, MD | 3.4 mi |
| 21163 | Woodstock, MD | 3.5 mi |
| 21117 | Owings Mills, MD | 3.9 mi |
| 21208 | Pikesville, MD | 4.6 mi |
| 21104 | Marriottsville, MD | 5.4 mi |
| 21207 | Gwynn Oak, MD | 6.1 mi |
| 21153 | Stevenson, MD | 6.2 mi |
| 21215 | Baltimore, MD | 7.2 mi |
| 21071 | Glyndon, MD | 7.5 mi |
| 21136 | Reisterstown, MD | 7.7 mi |
| 21209 | Baltimore, MD | 7.7 mi |
| 21228 | Catonsville, MD | 8 mi |
Questions about 21133
What is the ZIP+4 code for 21133?
21133 is the five-digit ZIP code. The ZIP+4 adds four more digits that identify a specific delivery point — usually one side of a city block, a single building, or a group of PO boxes. Because those four digits change from address to address within 21133, you need to look up a specific street address to get them.
What city is 21133?
21133 is assigned to Randallstown, Maryland, in Baltimore County.
Do I need to use the ZIP+4?
It is optional for ordinary mail, but it speeds up sorting and it is required for most USPS bulk-mail postage discounts. Many address-verification and e-commerce systems also use ZIP+4 to confirm a delivery point exists.
Need thousands of these?
Upload a CSV and get ZIP+4, county, carrier route, and delivery-point data appended to every row — or call the API directly.